This invention relates generally to electroplating devices and techniques, and more particularly to devices and techniques for electroplating continuously from a solution on to a thin film of material.
In the art of electroplating, a metal is electroplated from a solution on to a work piece, the solution having an electrolyte and there being an anode provided within the solution to furnish the current.
Normally the electrical current for the cathode is applied to the work piece using a contact outside the solution. This is done in order to prevent the contact itself from becoming a work piece and causing a buildup of the plating material on the contact. In the case of relatively thick work pieces wherein the overall electrical resistance of the work piece is low, there is not a great problem involved in getting sufficient current to the work piece as it passes through the solution even at significant distances from the contact. However in the case of thin work pieces such as plating on thin film of material, and wherein the volume of the material on the work piece is small, there is a problem of rapidly diminishing current as distance from the contact increases. Expressed another way where the metal itself is thin enough or small enough to have a relatively high resistance there is rather inefficient plating accomplished at any appreciable distance from the cathode where the current is introduced.
Various plating devices and schemes are shown in the following U.S. Pat. Nos: 4, 721, 554; 4, 662, 997; 4 ; 3, 865, 701; 4, 305, 80; 4, 304, 653; 3, 579, 430; 2, 708, 181; and 2, 490, 055.